Electric lamp



Nov. 8, 1938. H. KREFFT ET AL 2,135,719

ELECTRIC LAMP Filed April 15. 1938 Inventors: Hermann KreF-Ft,

Willy Wilde, Kurblvarhe,

' iv Attorn e y.

Patented Nov. 8, 1938.

2,135,719 ELECTRIOLAMP Hermann Kreift, Berlin-Friedrichshagen, Willy Wilde, Berlin-Zehlen Berlin-Tempelhof,

dorf, and Kurt Larch, Germany, assignors to General Electric Company, a corporation of New York Application April 15, 1938, Serial No. 202,310

In Germany April 20, 1937 3 Claims.

The present invention relates to electric lamps and more particularly the invention relates to such lamps of the type comprising a sealed envelope having mounted therein a gaseous electric discharge lamp device and a ballast resistance connected in series with said discharge device.

In such devices the resistance is mounted in the space between the lamp container and the envelope and is in the form of a filament capable of being heated to incandescence by current flow therethrough during the operation of the dis-' charge device to supplement and complement the light emitted by said discharge lamp device. This is particularly desirable when the gaseous electric discharge lamp device contains a quantity of mercury the vapor of which is excited -to luminescence during the operation of the device since the light emitted by the filament is rich in red rays which complement the light emitted by the discharge device which is deficient in such rays. When the discharge device is of the high pressure mercury vapor discharge type it has been found necessary heretofore, in order to obtain a spectrally balanced light, -to design the lamp in such manner that more than 50% of the line voltage is dissipated in the series ballast resistance since the light output of the discharge device is from two to four times that of the filament on the same current consumption. Such a resistance is, of course, larger than that required for'the purpose of limiting current fiow in the/ discharge device. A fundamental fault with lamps of this type is that the voltage available for the discharge device does not permit operation of the device at its maximum efliciency.

.7 The object of the present invention is to provide an electric lamp of the above type which operates at a higher emciency and which emits light having, a better spectral balance than that emitted by prior lamps. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

The invention attains its objects by mounting in the envelope of the lamp an auxiliary filament connected across the terminals of, the electric lamp in parallel with the discharge device and the filament which serves as the series ballast resistance for said device. The various elements of the electric lamp of the present invention canbe so designed with respect to each other that each element can serve its function at maximum efliciency, for example, the discharge device can be designed to operate at maximum efiiciency on a given line voltage without regard to the light output of the series filament. While the series filament does not emit, in such a case, sufficient light to balance the light emitted by the discharge device the auxiliary fllament connected across the terminals of the lamp can be so designed that it supplies the required supplementary light during the operation of the lamp and operates at the most favorable temperature.

A particularly advantageous feature of the new electric lamp is its emission of light from the auxiliary filament immediately on the application of potential to the lamp. The heat emitted by the auxiliary filament rapidly raises the container of the discharge device to its operating temperature to shorten the starting period of said device.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a front elevational view.

Referring to the drawing the electric lamp device comprises a sealed envelope orbulb I2 having a high pressure mercury vapor discharge device mounted therein. The tubular container l of the discharge device consists of quartz or other vitreous material capable of transmitting visible and ultra violet light and having a high softening temperature. Said container I has two electrodes, 1 and 8 sealed therein, one at each end thereof, and an auxiliary starting electrode 9' ounte'd adjacent the main electrode 8. .Said

el'ejtrodes 'l and 8 are thermionic, activated electrodes and are heated'to an arc discharge supporting temperature during device by the discharge incident thereat. The discharge device has a starting gas therein, such as neon, argon or the like, at a pressure of about -1 to 10 mm. and a body of mercury in such amount that it is wholly vaporized during the operation of the device. Preferably the dimensions and the current load of the discharge device are such so that the vapor is at a pressure of more than 1 atmosphere and, preferably, in the order of 10 atmospheres during the operation of the device. The container I has two perforated septums l0 and II therein which serve to guide the constricted arc discharge between said electrodes 1 and 8 during the operation of the device.

Said container l is supported in said bulb 12 by metal bands 2 and 3 fastened to and insulated from the current leads 4 and 5 of the helically coiled filament 6. Preferably the bulb I2 consistsof a visible and ultra violet light transmitting glass and has an inert gas, such as nitrogen, therein. Two current leads l5 and it are the operation of the 1 fused into the press l4 of the fiared stem I 8 of the bulb I2. One end of the lead I8 is connected to the currentlead 4 and the other end thereof is connected to the contact ll of the base i1, 28 of the bulb l2. One end of the lead I8 is connected to the main electrode 8 by the band 2 and the lead I8 and the other end thereof is connected to the sleeve 20 of the base I7, 20. The auxiliary, starting electrode 9 is connected to the main electrode 1 through a high ohmic resistance 2|, and leads 22, 5 and 23.

When potential is applied to the lamp current flows from the contact I'I, through leads l5 and 4 to the filament 8, which serves as the ballast resistance for the gaseous electric discharge device, and to lead 8. During starting current fiows from the lead 5 over lead 22 through resistance 2| across the gap between auxiliary electrode 8 and the main electrode 8 and thence over the conductors l8, 2,- i 8 and I8 to the sleeve 28. When the auxiliary, starting discharge between the electrodes 8 and 9 has ionized the gas in the container l the main dischargebetween electrodes I and 8 starts and current flows from lead 8 over lead 23 across the gap between the main electrodes 1 and 8 through the conductors l9, 2, I 8 and I8 to the sleeve 20. a

In order to avoid overloading of the series filament 8 during the starting of the gaseous electric discharge lamp device a high ohmic resistance connected in series with said filament 8 and which is short circuited by a bimetallic switch or a resistance having a negative coeflicient of electrical resistance, such as a uranium dioxide resistance, when the discharge device is operating at equilibrium is used, when desired. An arrangement of this type is disclosed in copending application Serial Number 136,447, filed April 12, 1937. When desired, part of the filament 8 is short circuited by the switching or resistance means disclosed above during the operation of the lamp as disclosed in the Patent Number 2,020,737, issued November 12, 1935.

An auxiliary incandescent filament 24 supported by wires 28 is mounted in said bulb l2 above said filament 8 and concentric with, the container l of the gaseous electric discharge lamp device. Said filament 24 is connected to the contacts l1 and 20 of the base by leads 4 and I8 and leads l8 and I 8 respectively. The auxiliary filament 24 is thus connected in parallel with both the series filament 8 and the gaseous electric discharge device and the full line voltage is applied thereto.

Preferably one half of the line voltage is dissipated in the discharge device and the other half in the series resistance 8. The current consumption of the discharge device and the series filament 8 is the same but the light-output of the discharge device is about two and one-half times that of the incandescent filament. If the discharge device has a light-output of lumens, for example, then the filament 8 has a lightoutput of 40 lumens. Since the light emitted by.

the discharge device contains practically no red rays and the light emitted by the filament 8 contains about 25% of red rays, that is, about 10 lumens, then of the lumens emitted by the lamp only 10 luniens,.or 7%, is red whereas daylight contains 12 to 15% of red., Preferably the auxiliary filament 24 is so dimensioned that it consumes about half as much current as the circuit consisting of the series filament 8 and the gaseous electric discharge lamp device. The voltage across the filament 24 is twice that across the filament 8 and the filament 24 emits 40 lumens of light, about 101umens of such light being red rays. The total light-output of the lamp is thus lumens and contains 20 lumens of red rays which constitute 11% of the total lumen out-put. The light emitted by the lamp is thus a close approximation of daylight and the lamp is useful for illumination purposes generally. It will be understood, that the above figures are used for example only, the actual lumen output of the lamp and its light emitting parts being much higher than that given in the example.

While we have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes the broad spirit and scope .of the invention, for

example, the bulb l2 consists of matte glass to diffuse the light and avoid glare, when desired.

What we claim as new and desire to secure by Letters Patent of the United States, is:-

1. An electric lamp comprising an hermetically sealed envelope, a gaseous electric discharge lamp device mounted in said envelope, a filament connected in series with said discharge device to serve as a ballast resistance therefor and another filament connected in parallel with said discharge device and said series filament, both of said filaments being mounted in said envelope and external to said discharge device.

2, An electric lamp comprising an hermetically sealed envelope,'a gaseous electric discharge lamp device mounted in said envelope, a filament connected in series with said discharge device to serve as a ballast resistance therefor and another filament connected in parallel with said discharge device and said series filament, both of said filaments being mounted in said envelope concentric with and external to said discharge device.

3. An electric lamp comprising an hermetically sealed envelope, a gaseous electric discharge lamp device mounted in said envelope, a filament connected in series with said discharge device to serve as a ballast resistance therefor and another filament connected in parallel with said discharge device and said series filament, both of said filaments being mounted in said envelope and external to said discharge device and means in said envelope toshort-circuit part of said series filament during the operation of said lamp device.

HERMANN KREFF'I. WILLY WILDE. KURT LARCHE. 

